Control apparatus for blood pressure testing device

ABSTRACT

A valve arrangement for accurately controlling the bleed rate of a sphygmomanometer. The valve includes a head mounted for movement between closed and open positions, with the open position being established by the setting of a cam element which is contacted by the head when the valve is opened. Contact between the head and the cam permits the air under pressure to escape from the sphygmomanometer either at a uniform rate (if the head-cam contact is maintained continuously) or in discrete controllable quantities (if the head is periodically brought into contact with the cam). The cam position is pre-settable to establish a range of release rates. The valve arrangement also incorporates an improved inverted conical release valve and seat.

[ June 12, 1973 CONTROL APPARATUS FOR BLOOD PRESSURE TESTING DEVICE [76] Inventor: Roger Hayes, 260 Garth Road,

Scarsdale, NY. 10583 [22] Filed: Oct. 26, 1971 [21] Appl. No.: 192,193

[52] US. Cl. l28/2.05 G, 251/285 [51] Int. Cl A6lb 5/02, Fl6k 51/00 [58] Field of Search 128/205 C, 2.05 G,

[56] References Cited UNITED STATES PATENTS 2,934,061 4/1960 Speelman 128/205 G 3,119,449 1/1964 Price 251/285 X 3,342,451 9/1967 Matousek 251/285 X 3,043,556 7/1962 Noland 251/285 X 3,504,663 4/1970 Edwards.... 128/205 .G 3,254,671 6/1966 Berliner 137/565 2,603,210 7/1952 Puig 128/2.05 G 3,375,823 4/1968 Pamplin et al.... 128/173 R 3,086,501 4/1963 Nielsen 251/285 X 3,613,667 10/1971 Beck U 128/205 G 3,361,148 l/l968 Turek 251/285 FOREIGN PATENTS OR APPLICATIONS 661,575 3/1929 France 128/205 G Primary Examiner-Kyle L. Howell A ttorney-George Gottlieb, Michael 1. Rackman and James Reisman et al.

[5 7] ABSTRACT A valve arrangement for accurately controlling the bleed rate of a sphygmomanometer. The valve includes a head mounted for movement between closed and open positions, with the open position being established by the setting of a cam element which is contacted by the head when the valve is opened. Contact between the head and the cam permits the air under pressure to escape from the sphygmomanometer either at a uniform rate (if the head-cam contact is maintained continuously) or in discrete controllable quantities (if the head is periodically brought into contact with the cam). The cam position is pre-settable to establish a range of release rates. The valve arrangement also incorporates an improved inverted conical release valve and seat.

22 Claims, 9 Drawing Figures CONTROL APPARATUS FOR BLOOD PRESSURE TESTING DEVICE This invention relates to pressure control mechanisms and in particular, to a valve for controlling the release of air from a blood pressure testing device or sphygmomanometer.

In recent years, medical science has made numerous advances both in the diagnosis and the treatment of many diseases. While many of these advances stem from the work of pure research, important contributions are regularly made in the area of instrumentation as well. In fact, without new developments in apparatus to accompany the research work, the advances in diagnosis and treatment of diseases could not readily be made available to the general public.

It has also become well known that one significant area for research and diagnosis is a patients blood pressure. Measurement of this characteristic has long been recognized as important in determining the possible presence of or tendency towards several diseases, including heart disease and strokes. With heart disease in particular being responsible for more deaths in the United States than any other single disease, it is of para mount importance to have reliable blood pressure testing devices which promote accuracy and minimize error in measuring blood pressure.

While the prior art has of course been aware of this need for some time, theequipment devised to meet this problem has not been completelysatisfactory. The traditional sphygmomanometer used by doctors and nurses accomplishes the task of measuring blood pressure, but often such measurements are not as accurate as they should be, or else the manipulation of the equipment by the attendant requires too much direct concentration and attention, thereby restricting other functions which may need to be fulfilled by the attendant while the device is being used.

An important parameter in prior art devices of this type is the rate at which the pressurized air in the blood pressure cuff (wrapped around the patients arm) is released. Nearly all of the prior art devices provide for releasing air at a controlled rate, but they also depend on the attendants dexterous manipulation of a variable release valve which usually takes the form of a screw knob or push button. The mode of operation of all sphygmomanometer valves developed to date, then, requires the operator to adjust a continuously variable valve to establish the proper bleed rate during the blood pressure determination this requires the attendant to focus his attention on the release valve setting instead of on the subjects condition. Also, since the escape rate can be varied over a wide range, poorly adjusted valve settings can lead to attendant strain and what is worse, can result in less accurate blood pressure determinations when the air is released too fast. in these prior art arrangements, since the escape rate can vary over an extremely wide range, it is very difficulat to either maintain a uniform escape rate throughout the measuring cycle, or to re-establish such a uniform rate if the deflation control is ever returned to its closed position.

The use of such prior art analog"-type devices is a distracting handicap to operators because the establishment of'corrcct and uniform deflation rates is quite difficult to achieve without the operator's paying careful attention while the air is being released. The rate needs to be high enough to obtain the two critical pressure readings (systolic and diastolic points) without unnecessary delay, yet it cannot be so high as to bypass those points without permitting the operator to note them precisely. With prior art equipment, each measuring cycle is a completely new run, with little or no likelihood that the operator will, except by precise manipulation, establish the desired and optimum bleed rate. Accordingly, the absence of any arrangement for obtaining uniform bleed rates which may suit a particular operator is one major problem which the prior art has not solved.

In addition, the prior art does not include the capacity of allowing the release of air in discrete quantities, i.e., in a stepped fashion without losing the bleed setting. The operator has not been heretofore provided with the facility of stepping the pressure down gradually to thereby approach or zero in on the two critical pressure reading points. This same failing of the prior art causes it to be unable to pause during the measuring cycle at any given point (e.g., after one reading has been taken but before the other has been reached) and to then resume the cycle at the same bleed rate when the operator chooses to do so. The prior arts approach to this problem has been to rely solely on the operator for control of the bleed rate, and this generally necessitates the operators paying too much attention to the measuring cycle, and does not avoid the possibility of an overly rapid escape rate and thus inaccurate pressure readings.

It is therefore an object of this invention to obviate one or more of the aforesaid difficulties.

It is another object of this invention to precisely control the rate of release of air from a blood pressure testing device.

It is a further object of this invention to provide variable pre-determination of the bleed rate for a blood pressure testing device so that an operator canpreselect an optimum release rate which remains unchanged until the operator chooses to change it.

It is also an object of this invention to allow a sphygmomanometer to be deflated rapidly without operator attention, or to stop the deflation at pre-deterrriined settings and then resume the same deflation rate as the pressure is reduced.

Additional objects and advantages of this invention will become apparent when considered in conjunction with one particular illustrative embodiment of the invention, wherein a valve body includes a control head capable of assuming a plurality of variable, pre-settable positions to establish the bleed rate in a blood pressure testing device. The main section of the valve body couples the conventional inflating bulb of the sphygmomanometer to the blood pressure cuff which is generally wrapped around the patients arm in order to take the pressure readings. Between the bulb and the cuff is the control portion of the valve head the normal position of the head is such that there is no interruption of the air flow between the bulb and the cuff, thereby permitting the cuff to be inflated in the normal manner. The bulb is periodically squeezed by the operator to cause air to fill the cuff, and the air passes through an axial bore in the valve body and dislodges a check valve at the input side of the body to cause air to be transferred into the cuff to build up the pressure therein.

The valve control head of the invention includes upper and lower segments within which the valve stem is received the upper portion of the stem is threaded into the upper and lower segments of the head and is thereby locked in place, establishing a fixed position for the stem during operation of the valve. The bottom of the valve stem is shaped in the form of an inverted cone and is received within a correspondingly shaped valve seatsurrounding that portion of the stern. In the normal position where the valve is not operated (and air is not being released from the cuff), the tight engagement between the bottom of the valve stem and its seat prevents the escape of any air from the cuff and allows air to pass only from the bulb to the cuff during the inflation process.

The lower segment of the valve control head, in addition to providing an axial bore for the valve stem, also includes an internal chamber which is vented to atmosphere and which houses a spring which controls the vertical movement of the head. Normally, one end of the spring lodged within this chamber bears against an upper wall thereof, while the other end of the spring bears against the upper wall of a stationary element threaded into the main portion of the valve body this biases the control head into an upper position. In this position, the inverted conical portion of the valve stem bears against its seat and prevents the escape of air from the blood pressure cuff to the spring chamber in the lower segment of the valve head and through the opening therein to the atmosphere.

In its normal closed position, the lower surface at one side of the valve head is positioned above a cam or stop element which in one embodiment is mounted in a circumferential slot in the valve body. The cam is eccentric with respect to its center of rotation, and is in the slot in the valve body so as to be rotatable about the longitudinal axis of the valve body. Accordingly, the radial distance from the axis of the valve body to the outer circumference of the cam varies depending upon where along the cams circumference the radial distance is measured. As the cam is rotated, the eccentricity thereof varies with respect to the valve head position thus, the distance between the lower surface of the valve head and the upper surface of the cam beneath the valve head varies from a minimum (when the largest radial segment of the cam is positioned beneath the head) to a maximum (when the narrowest radial segment of the cam is beneath the head). This establishes different stroke distances for the valve head which comes into contact with the underlying cam when the head is depressed against the action of the in ternal spring.

If the cam element is set with a relatively wide portion of the cam beneath the head, the stroke of the valve head will be relatively small and this will establish only a correspondingly small opening between the valve stem and its seat. Thus, while a complete passageway for air will be established from the cuff through the valve body, past the seat and longitudinally along the valve stem to atmosphere through the spring chamber, it will be a path of relatively small area permitting only a relatively slow escape rate. The pressure will thereby be reduced quite gradually. lf, on the other hand, the cam is adjusted so that a relatively narrow radial segment thereof is brought into position under the control head of the valve, the stroke distance for the head will be relatively large, and depression of the head will cause the enclosed valve stem to be separated from its seat by a relatively large dimension. This will establish a much greater flow rate for the pressurized air in the cuff, which will then pass to atmosphere over the previously noted path at a much greater rate. Thus, as long as the head is maintained in the depressed condition, the pressure in the cuff will be reduced at a relatively more rapid rate.

It is of great significance that the cam can be set in a variety of positions simply by rotating it in its mounting slot in the valve body. This places different radial segments of the cam into position beneath the control head and thereby establishes a great variety of possible stroke distances for the valve head when it is to be depressed by the operator. The setting of the cam remains fixed once it is rotated into a given position (until changed by the operator), and the stroke distance of the head is correspondingly fixed at such times. Accordingly, the control head can be maintained in the depressed condition continuously by the operator, thereby maintaining the uniform deflation rate for the cuff. At the operators discretion, the pressure can be reduced in'discrete quantities by alternately depressing and releasing the control head this causes the head to move from the depressed position (in contact with the cam element) to the normal closed positionin response to the action of the spring. This affords the operator the option of lowering the pressure in discrete quantities while observing the reduction caused thereby on the pressure gauge. In this manner, the operator may establish his own preferred reading rate and procedure and can obtain more accurate pressure readings.

If it is desired to pause during the measuring cycle, the attendant merely releases the control head, which then returns to its normal closed position, shutting off air flow and halting the reduction in pressure. When the cycle is to be resumed, depression of the control head causes it to travel a distance identical to that previously travelled, coming into contact with the pre-set cam at the same precise position as during the previous portion of the measuring cycle. This re-establishes the same escape rate for air from the cuff, and the measuring cycle can then continue at the proper rate. No attention need be paid by the operator to the reestablishment of the same bleed rate, other than the simple depression of the control head, which is then brought into contact with the pre-set cam element.

The control head's lower segment includes a beveled portion on its outer surface, which portion is normally facing away from the underlying cam. When the head is being used as described above during normal bleeding of the cuff to obtain the pressure readings, the beveled surface of the head is not utilized. However, when the two critical pressure readings have been taken and there is no longer any need to lower the cuff pressure at a controlled or even a stepped-down rate, the control head is rotated about its vertical longitudinal axis to bring the beveled surface into position above the cam element. The operator then depresses the head, and the lower surface of the head clears the upper projecting portion of the cam because its radius is reduced at the point of the bevel. However, as the head continues to be depressed, the cam makes contact with the beveled surface of the head and a force-fitting relationship between the head and cam is established. This retains the valve head in a lowermost depressed condition withoutany further action on the part of the operator. Because of the establishment of this position, the valve stem is separated from its seat by the maximum distance, thereby producing the highest escape rate for air from the blood pressure cuff. Accordingly, the air escapes along the previously indicated path into the atmosphere at a high rate, thereby quickly reducing the pressure in the system to zero without any operator attention. When all the air has escaped from the cuff, indicating the end of the measuring cycle, the operator can elevate the control head to withdraw it from the force-fitting contact with the cam. Under the influence of the internally housed spring, the head returns to its normal elevated position, with the valve stem engaged with its seat, thereby blocking the escape of air from the cuff, leaving the bulb-cuff air passageway ready for the next inflation cycle. As a final step, the valve head is rotated about its longitudinal axis to return the beveled portion to its original position where it will not come into contact with the cam upon depression of the head.

It is therefore a feature of an embodiment of this invention that a valve head in a sphygmomanometer is movable between a fixed closed position and a plurality of variable and pre-settable open positions.

It is a further feature of an embodiment of this invention that the open position of a sphygmomanometer valve head is established by the setting of a variable cam or stop element.

It is another feature of an embodiment of this invention that a sphygmomanometer valve head is rotatable about its axis to bring a beveled surface thereof into engagement with an adjustable cam to fix the position of the head and to provide for a constant and rapid bleed rate.

It is also a feature of an embodiment of this invention that an inverted conical valve and a corresponding inverted conical valve seat control the release of air in a blood pressure measuring device.

Additional objects, features and advantages of the present invention will become apparent when considered in conjunction with a presently preferred, but nonetheless illustrative, embodiment of the invention as explained in the following detailed description and as shown in the accompanying drawing, wherein:

FIG. 1 is a perspective view of a portion of a sphygmomanometer including the inflation bulb and the control valve, illustrating the cam and head elements;

FIG. 2 is a front sectional view of the valve of the invention showing the head in closed and open positions, and taken from the perspective of line 2--2 of FIG. 1 in the direction of the arrows;

FIG. 3 is an end view of the valve control mechanism of the invention, partly in section, taken along the line 3-3 of FIG. I in the direction of the arrows;

FIG. 4 is an exploded view of the component parts of the valve and valve body of the invention;

FIG. 5 is a view of the valve head in a depressed condition whereby it is in a force-fitting engagement with the'cam;

FIG. 6 is a fragmentary view of the valve stem portion of the invention illustrating an alternate form of valve seat therefor;

FIG. 7 is a perspective view of a portion of a sphygmomanometer having an alternative cam embodiment;

FIG. 8 is a top view of a portion of the sphygmomanometer embodiment of FIG. 7; and

FIG. 9 is a front view, partly in section of a portion of the valve and alternative cam embodiment of FIG. 7.

The drawings illustrate the invention in connection with a conventional sphygmomanometer, including the inflation bulb and hose connections to other portions of the device which are not illustrated for example, the pressure gauge from which the pressure readings are'taken and the case in which the mechanism is carried are not illustrated herein. However, those portions of a typical sphygmomanometer may be referred to during the course of this description and they may be assumed to operate in the normal manner. The overall invention is illustrated in FIG. 1, where a valve and control mechanism 10 is shown. Included in this showing are the valve control head 12, the variable position cam 14 and main valve body 16. The far end of valve body 16 includes a hose connection 18 which is coupled to the blood pressure cuff, represented by block 17, to be wrapped around the patients arm during the measurement cycle. The other end of the valve body is coupled by means of hose 20 to inflation bulb 22 which is of a conventional type and is squeezed by the operator to gradually inflate the blood pressure cuff.

Considering FIGS. 1 and 2 together, valve head 12 includes an upper cap section 24 and a main lower section 26. The upper section 24 and the lower section 26 include threaded bores 240, 26c respectively which are arranged to mate with external threads 28a of valve stem 28. Valve stem 28 terminates at its lower end in inverted conical portion 28b which normally resides in flush engagement with correspondingly shaped valve seat 30. This precludes the passage of air upward along the passageway 32 surrounding the lower portion of valve stem 28 and thence into chamber 34 and escaping to atmosphere through channel 38. The inverted conical stem portion 28b and seat 30 are particularly advantageous because they cooperate to provide an airtight seal over a wider surface than did the prior art. The prior arr generally relied on contact between the stem and a relatively sharp ridge, and this often led to a portion of the stem being worn away, causing leakage problems and inaccurate readings. Another advantage of the present conical seat and valve stem as applied to a depressable valve is the provision of an opening which is substantially proportional to the travel of the valve stem the prior art openings are not controlled in this manner, and provide instead a non-linear opening which is much less desirable.

Valve head 12 is maintained in its upper closed position by the action of spring 36 which is slightly compressed as illustrated in FIG. 2. In this condition, spring 36 bears against fixed lower wall 34a of chamber 34, and urges head 12 upwards by contact with upper wall 34b of chamber 34. Valve head 12 will be urged upwardly until limited by the engagement of valve stem portion 28b with seat 30. This fixes the position of valve head 12, which is maintained in this upwardly biased position in response to the action of spring 36. When head 12 is depressed by an operator, this disengages inverted conical valve stem portion 28b from corresponding seat 30, moving it to position 28b, and permits air to pass from block 17, hose coupling 18 and bore 16b upward past stem portion 28b and into chamber 34. In order to maintain the depressed position of valve head 12, the action of spring 36 must be overcome by the operator, who generally will keep his thumb on the top of cap portion 24. This causes the lower surface 12a of segment 26 to come into contact with the upper surface of cam 14 as illustrated by the phantom head showing at 12 in FIG. 2. Air thereby escapes from the blood pressure cuff through aperture 38' as indicated by the arrow. The operators release of downward pressure on valve head 12 will return the head to the position in full line in FIG. 2, thereby closing off the port to atmosphere through channel 38.

Considering FIGS. 2 and 4 in conjunction, it is seen that the position of valve stem 28 in its vertical travel is established by the threading of upper portion 28a thereof into segments 24 and 26 of head 12 cap 24- is threaded onto stem portion 28a and is rotated opposite to segment 26 to produce integral head 12. When valve head 12 is depressed thereafter, stem portion 28b is disengaged from valve seat 30 (FIG. 2). and clears downward through washer 42, reaching a lower position within receptacle 44a of fixed valve-receiving cup 44. The path for escaping air is thus established within cylindrical bore 32 of element 40 which is screwed into valve body 16 by means of threads 40a. Valvereceiving cup 44 acts as a rearward stop for check valve 46 when air is being directed from bulb 22 to the left through bore 16a. This dislodges check valve 46 from the position illustrated in FIG. 2, and moves it to the left until it contacts the right upper projecting surface of valve-receiving member 44. Air is then-passed into bores 16c and 16b and via hose coupling 18 into the blood pressure cuff.

A TYPICAL OPERATING CYCLE OF THE INVENTION 1. Inflation of the Cuff With the valve in the position illustrated in FIG. 1 and with head 12 in the position shown at full line in FIG. 2, the inflation cycle takes place. (The operator will have already set cam 14 at the proper position to establish the desired depression distance for valve head 12 during the deflation'cycle, but this will be referred to below.) In order to establish a sufficiently high pressure in the blood pressure cuff in accordance with conventional blood pressure reading techniques, it is necessary for the operator to repeatedly squeeze bulb 22 to elevate the pressure in the cuff to a point which is well above the highest pressure reading expected from that particular patient. Then, in accordance with standard practices, the pressure will be lowered as will be described below to arrive at the two critical blood pressure reading points.

In order to elevate the pressure in the blood pressure cuff, bulb 22 is repeatedly squeezed and released, forcing air along the path indicated by the solid line arrows pointing to the left in FIG. 2, that is, through hose 20, past filtering screen 50 and into bore 16a of valve body 16, and then drawing air into bulb 22 through conventional one-way inlet 22a. Check valve 46 is movably fitted within enlarged bore 160 of valve body 16, but this snug fit is overcome by the introduction of air under pressure from bulb 22. Accordingly, check valve 46 is dislodged to the left, such that its forward conical end 46a is disengaged from corresponding circumferential valve seat 48. The air under pressure from bulb 22 is thereby permitted to pass to the left in FIG. 2 through the small space between check valve 46 and bore 16c. Check valve 46 is dislodged to the left in FIG. 2 to the point where it comes into contact with valve-receiving cup 44, and it is maintained in this position as long as air is being supplied to inflate the cuff by virture of the squeezing of bulb 22.

After the air under pressure from bulb 22 has dislodged check valve 46 as previously described, the air passes into bore 16b (which is essentially an extension of bore 16c), and passes out of valve body 16 into hose coupling 18. From hose 18, the air is connected to the blood pressure cuff, represented by block 17, which is accordingly inflated to an appropriate high level by repeated squeezings of bulb 22. When the correct level of pressure is reached, the operator ceases the squeezing of bulb 22. During the entire inflation process, air caan only pass to the left from hose 20, through bores 16a and and into bore 16b leading to hose 18. There is no other escape path for the air, and particularly none is available through valve head 12, since valve stem portion 28b is flush-fitted with its valve seat 30, thereby precluding the upward passage of air to chamber 34 and thence to escape channel 38.

2. Deflation Cycle Usually at sometime prior to the actual commencement of deflation of the blood pressure cuff in order to take the blood pressure readings, the attendant has set the predetermined desired deflation rate by manipulating eccentric cam 14. As shown in FIG. 4, cam 14 is mounted in slot 16d of valve body 16 with gap 14a facilitating such mounting. The cam is rotatable about the central core of valve body 16, around which is fitted aperture 14b of cam 14. The deflation rate can be set in accordance with the attendants own specifications, and can range from a maximum bleed rate corresponding to the maximum depression of valve head 12, to a minimum bleed rate based upon the minimum depression of valve head 12. The depression of valve head 12 is controlled by the attendants manually depressing valve head 12 against the action of spring 36, and this will generally be accomplished with the thumb of the attendant as bulb 22 is held in the palm of the attendants hand.

The stroke of valve head 12 is dependent upon the distance identified in FIG. 2 as L, and represents the distance between the lower right-hand surface 12a of valve head 12 and the upper surface of the circumference of cam 14. When these surfaces come into contact by depression of valve head 12 as illustrated in the phantom position of the valve head at 12 in FIG. 2, the extent of the depression of valve head 12 is established and the lower portion 28b of valve stem 28 is unseated from its corresponding seat 30 by the distance L, and moves to position 28b to permit the passage of pressurized air from the cuff to escape to atmosphere through channel 38. Referring to FIG. 4, the maximum radial thickness of cam 14 is identified as X, while the minimum radial distance is identified as Y. These two locations on cam 14 establish the minimum and maximum stroke distances of valve head 12 respectively when cam 14 is rotated so that dimensions X and Y are at the uppermost position of cam 14, i.e., directly beneath surface 12a of valve head 12. For example, in the end view illustrated in FIG. 3, dimension Y of cam 14 is positioned beneath surface 12a of valve head 12, thereby establishing the maximum stroke distance for valve head 12 and the maximum bleed rate for the pressurized air from the cuff.

A wide range of settings to establish different bleed rates is available with this invention, based upon rotating cam 14 to various positions between dimensions X and Y. Each one of these different cam settings represents a different distance L through which valve head 12 will travel downwardly before making contact between its lower surface 12a and the upper tangential surface of cam 14 as shown in FIG. 2. The availability of these different settings is a great advantage, since the attendant will be able to cause air to be released from the blood pressure cuff at a rate which permits that particular attendant to properly and satisfactorily take the necessary readings. Thus, one attendant may find it desirable to release the pressurized air at a relatively rapid rate, and therefore he will set cam 14 with its dimension Y beneath surface 12a of valve head 12; on the other hand, an attendant may not be as practiced in taking these readings and may wish to release the air more slowly so as to insure that the two critical pressure points are not missed as the pressure is lowered such an attendant will undoubtedly select a setting of cam 14 closer to dimension X. In any event, the attendant can pre-select his chosen release rate at a convenient time. Thereafter, regardless of which cam setting is selected, the controlled release of air is established by the operators depressing valve head 12 against the action of spring 36 and maintaining the contact between valve head surface 12a and the upper tangential surface of cam 14. As long as this contact is maintained, air from the blood pressure cuff will continue to be released as will be described below; the operator can also interrupt the release of air by permitting valve head 12 to return to its normal position as illustrated in FIGS. ll-3, thus preventing air from being released from the blood pressure cuff. Then, when the valve head 12 is again depressed and contact is made between its surface 12a and the upper surface of cam 14, the identical rate of release of air will again be established this capability of reestablishing the precise release rate following an interruption in the bleeding of air through the valve is a significant advantage of this invention and has not been present in the prior art.

When cam 14 has been set in accordance with a particular operators preference for establishing a desired release rate, the actual release of air from the blood pressure cuff is achieved by depressing valve head 12 from the full line position illustrated in FIG. 2 to the phantom line position at 12. Valve head 12 travels through the stroke distance L and its lower surface 12a makes contact with the upper tangential surface of cam 14 which is beneath surface 12a. Since valve stem 28 is integral with valve head 12 due to the threading of male segment 28a into female threaded segments 24a and 26c, the depression of valve head 12 also causes valve stem 28 to be lowered. Inverted conical segment 28b of valve stem 28 is thereby separated from valve seat 30; the engagement of segment 28b and seat 30 had previously prevented air from escaping towards chamber 34. When a passageway is established around valve stem portion 28b by the depression of valve head 12, air within the pressurized cuff is allowed to escape through that passageway (between stem portion 28b and seat 30) and up through the narrow cylindrical space identified as 32 in FIG. 2 and thence into chamber 34. The air then passes to atmosphere through escape channel 38'. It is noted that the air follows the path indicated by the dashed arrow lines pointing to the right within hose l8 and bore 16b and to atmosphere through channel 38' in FIG. 2. The air cannot travel to the right and into bore 160 because of the engagement of check valve 46 specifically, because of the air under pressure escaping from the cuff, check valve 46 is forced into engaging position such that its conical nose 46a is engaged within corresponding circular seat 48, thus blocking the passage of air from cylindrical bore 16c into bore 16a.

While valve 12 is depressed such that its lower surface 12a is making contact with the upper surface of cam 14 as shown in the phantom position at 12' in FIG. 2, the path by which air can escape around valve segment 28b and through bore 32 into chamber 34 and then to atmosphere through channel 38', is available. If the operator wishes a constant escape rate for the air from the blood pressure cuff, this is the position that will be maintained throughout the measuring cycle. By maintaining the contact between surface and cam 14, continuous bleeding of air from the blood pressure cuff at a uniform rate is achieved. However, it is possible that under certain circumstances, an operator may wish to either interrupt the escape of air from the cuff, or only to reduce the pressure in the cuff in discrete, stepped quantities. The present invention, in marked contrast to the prior art, is also capable of achieving this type of operation. For example, it may be desirable to interrupt the release of air from the blood pressure cuff as the upper or systolic pressure reading is approached while the pressure is being reduced. Thus, the operator may be aware of the approximate systolic point for a particular patient, and may wish to initially release air continuously at the predetermined rate established by the setting of cam 14 with respect to valve head surface 12a. Then, as the systolic point is approached, the operator would interrupt the release of air from the blood pressure cuff in order to zero in on the systolic reading point. This could be done by alternately depressing and releasing valve head 12, thereby causing it to move between the full line and phantom positions at 12 and 12 respectively in FIG. 2. This relatively rapid and periodic depression of valve head 12 will cause the pressure in the cuff to be reduced by a discrete quantity for each such depression. The operator will nevertheless be readily able to follow the pressure reduction on the conventional pressure gauge, and the systolic reading will be immediately apparent as the pressure is stepped down in this fashion.

Another possible reason for permitting valve head 12 to return to its full position in FIG. 2 during the pressure reading process is that after the systolic pressure reading is taken, the attendant may wish to pause briefly before resuming the readings to carefully record the systolic point. It is also possible that the attendant is monitoring a number of other bodily functions or is testing certain parameters of the patient whose pressure is being read, and it is occasionally necessary to temporarily interrupt the pressure reading to supervise these other activities. With the prior art, the interruption of pressure readings often resulted in wasting an entire measuring cycle, requiring the operator to again inflate the bulb and commence pressure reduction. However, with the present invention, once the systolic pressure reading point has been observed and possibly recorded, the pressure reading cycle can be interrupted as indicated above by releasing valve head 12, and then can be resumed so as to again observe the pressure gauge to obtain the diastolic pressure point. Observation of the diastolic pressure point can also be obtained by the operators continuous release of pressure from the cuff with valve head 12 in continuous contact with cam 14; or, the diastolic point can also be observed by the zeroing in" approach whereby valve head 12 is alternately depressed and released, thus causing valve stem segment 28b to be alternately engaged and disengaged with respect to its seat 30. Air is thereby again released in periodic stepped fashion and the diastolic pressure reading can be observed by the operator. Of course, at any point, the operator can again resume the continuous release of air from the cuff by depressing valve head 12 into contact with cam 14 and maintaining the contact for as long as desired.

3. The Rapid Deflation Mode Subsequent to observation of the two critical blood pressure reading points, whether obtained on the basis of a continuous release of air or a stepped-down reduction, as described above, it is desirable for the operator to be capable of quickly releasing all of the remaining air under pressure in the blood pressure cuff in an unattended manner. As will be recalled from a consideration of FIGS. 2 and 4, the maximum rate at which air can be released from the blood pressure cuff will occur when the dimension L is at its greatest, and this in turn exists when cam 14 is set with its Y dimension (FIG. 4) at the uppermost position beneath valve head surface 12a, for example as is illustrated in the end view of FIG. 3. However, even this maximum bleed rate for the release of air from the blood pressure cuff (via hose l8, bore 16b and ultimately out to atmosphere through escape channel 38 as has been previously described) represents only a gradual reduction in pressure; if the operator were limited to this rate of pressure reduction after having taken the two critical readings, it would still be a relatively long interval (perhaps to seconds) before the cuff would be completely deflated. The present invention obviates this problem by providing a specific and convenient structural arrangement within the context of valve head 12 to provide rapid deflation of the blood pressure cuff. This arrangement relates principally to the left side of valve head 12 as illustrated in FIG. 2, namely beveled surface 264. As illustrated in the exploded view of FIG. 4, it is seen that beveled surface 26a represents a generally parabolicshaped area (formed by a plane obliquely intersecting the outer surface of valve head segment 26) however, this particular shape or arrangement for beveled surface 26a is merely illustrative, and various other shapes, sizes, angles and arrangements can also be utilized.

In actual use, surface 26a comes into play after the second or diastolic pressure reading is taken by the operator. With rapid deflation of the blood pressure cuff being desired at this point, the operator, illustratively utilizing the thumb and forefinger of the hand in which the bulb 22 had been held, rotates valve head 12 about its central vertical axis defined by valve-stem 28. This rotation is suggested by the curved arrow in FIG. 5. The

rotation continues until surface 26a is directly above cam 14, and this is essentially 180 from the position of valve head 12 illustrated in FIGS. l-3. As noted in FIG. 5, this brings normal contacting surface 120 of valve 12 to the left, so that it will not engage the upper tangential surface of cam 14 when valve head 12 is depressed. Following the 180 rotation of valve head 12, the operator then depresses valve head 12 to its maximum lowest point this point is defined by the contact point between beveled surface 26a and cam 14, and is identified in FIG. 5 as 2612. In depressing valve head 12, it is noted that spring 36 becomes quite compressed within chamber 34, but this spring action is overcome by the wedging contact between surface 26a and cam 14 at region 26b. When this wedging or force-fitting relationship has been established, valve head 12 will remain in its lowermost depressed condition without any further action by the operator, and with no need for the operator to maintain any downward pressure on valve head 12.

This lowermost depressed position of valve head 12 represents the maximum excursion for valve head 12 and is lower than the previously described lowest point of valve head 12 when its surface 12a came in contact with cam 14 (FIG. 2). With this maximum downward point for valve head 12, the maximum escape rate of air from within blood pressure cuff is also established. The path which the escaping pressurized air follows is essentially the same as that usually followed, since the l rotation of valve head 12 merely reorients escape channel 38, but does not change the path followed by the escaping air. Thus, considering FIGS. 2 and 5 together, the air travels from the cuff through hose 18 and into bore 16b, and then, with the conical passageway established by seat 30 being totally free since valve stem portion 28b is received within region 44a of cuff 44, the air in relatively larger quantities is free to pass'upward through annular region 32 as it passes valve stem 28 and moves into chamber 34 and out to atmosphere through escape channel 38, which in this case is facing to the left as indicated in FIG. 5. Because of the relatively great downward movement of valve head 12 until surface 26a contacts cam 14, the opening or spacing between valve stem 28b and seat 30 is considerably larger than that which existed when valve head surface 12a contacted cam 14 (even when dimension Y of cam 14 was in position). Accordingly, the air from the blood pressure cuff escapes to atmosphere through channel 38 almost immediately upon establishment of the wedging contact between surface 26a and cam 14, and the operator need not hold the valve head down during this rapid deflation process.

When the deflation has been completed, as determined by the operator, and at his convenience, valve head 12 can be elevated from the position illustrated in FIG. 5 to release the wedging contact between surface 26a and cam 14. Once this release has been effected, spring 36 causes valve head 12 to return to its normal uppermost position. The operator then only need rotate the head 12 back to the position illustrated in FIGS. l-3 to prepare the invention for the next measuring cycle. This rapid deflation arrangement is readily accomplished without any significant amount of attention being paid to it by the operator, and permits a much more rapid release of air from the blood pressure cuff than would normally be possible using the basic apparatus of the invention.

In FIG. 6, a fragmentary showing of a portion of the invention is given, with an alternate embodiment of the valve stem and seat arrangement. Specifically, it is noted that while valve stem segment 28b is the same conical shape as previously described, valve seat 30' is recessed upwards into threaded block 40. When valve stem 28 is in the normal closed position as shown in FIG. 6, the blockage of air from the blood pressure cuff is the same with the embodiment of FIG. 6. However,

when valve head 12 is depressed causing valve stem 28 to move downward within block 40, stem portion 2812 also moves downward into the substantially cylindrical space defined by seat 30'. As valve stem portion 28b moves further downward (e.g., through washer 42), a wider opening for air to pass upward into annular region 32 is established. This wider area, permitting higher escape rates for air from the blood pressure cuff, is based on the existence of a longer stroke distance for valve stem 28. This valve stem and seat configuration could prove a desirable alternative for ease of manufacture. As can be appreciated from consideration of FIGS. 2, 4 and 6, for example, the alternate embodiment of valve seat 30 can be utilized merely by unscrewing block 40 from valve body 16, and replacing valve head 12 and its internal parts with a comparable valve head and block 40 having therein the valve seat construction illustrated at 30' in FIG. 6.

In the foregoing description, cam 14 has been illustrated as a disc rotating in a circumferential slot around the valve body. It should be understood that the present invention also encompasses other specific embodiments for the cam, such that variable but pre-set stroke distances L can be established for valve head 12. For example, the cam may take the form of a vertically mounted truncated cylinder, i.e, a cylinder whose longitudinal axis is parallel to stem 28 and which has an elliptical upper surface formed by a plane cutting through the cylindrical cam at an oblique angle. Such a truncated cylindrical cam would be located substantially in the position occupied by disc 14, and would variably interrupt or stop the downward movement of valve head 12 by contact between the lower near edge of segment 26 of head 12 and the oblique elliptical surface of the cam. By rotating the cylindrical cam about its vertical axis, a range of stroke distances L could also be established to define different escape rates from the blood pressure testing device.

This cylindrical cam embodiment is illustrated in FIGS. 7-9. Referring initially to FIG. 7, in which comparable parts bear the same reference numerals as in FIGS. l-o, cylindrical cam 13 is shown as being mounted on valve body 16. Cam 13 is rotatable about a vertical axis which is parallel to the axis of rotation of head 12. As can be appreciated from a general consideration of FIG. 7, the upper angled surface of truncated cylindrical cam 13 can be disposed at varying orientations beneath head 12, thereby establishing different downward travel distances for the head. If the highest point of cylinder 13 is rotated to a position under head 12, 'the head will travel downward for a relatively short distance and will thereby establish a relatively slow release rate for the pressurized fluid; on the other hand, if the shortest vertical segment of cylinder 13 is disposed beneath head 12, a larger downward travel distance for the head will be established, thereby causing a comparably greater fluid release rate. The view of FIG. 8 illustrates the overhanging relationship between head 12 and cylinder 13.

Cylinder 13 is mounted on valve body 16 by means of bolt 13b, which, as seen in FIG. 9, is arranged not to project beyond the truncated surface 13a of the cylinder. The bolt 13b can be tightened into a female threaded receptacle in valve body 16 which is designed to accommodate the threads on bolt shaft 130. To permit cylinder 13 to rotate about bolt 13b, a spring washer 13d is included between the bolt head and the bottom of the bolt head receptacle as shown in FIG. 9.

By rotating cylindrical cam 13 about its vertical axis, different portions of surface 13a are brought beneath head contacting surface 12a, as shown in FIG. 9. This establishes an operating range of travel distances for head 12, a typical one of such distances being designated as L in FIG. 9.

As described above, the invention is thus seen to represent a specific but substantial improvement in the taking of blood pressure readings, one of the principal advantages thereof being the freeing of the operator from the necessity of paying any significant attention to establishment of the optimum bleed rate or its reestablishment should the measuring cycle be interrupted, either accidentally or intentionally by the operator. The invention provides for establishing a reasonable range of escape rates which can be set by the operator in accordance with his own convenience, possibly based in part upon a particular patients blood pressure record. Different operators can utilize precisely the same apparatus and can pre-set the escape rate to their own specifications. The pressure reduction represented by the depression of valve head 12 can be obtained on a continuous basis by causing valve head 12 to remain in continuous contact with underlying cam 14, or the reduction can be effected in discrete downward steps based upon the alternate depression and release of valve head 12 as has been described. Finally, when the two critical blood pressure reading points have been observed and recorded by the operator, a simple rotation of valve head 12, followed by its depression into a wedging contact with cam 14, causes a maximum quick deflation rate to be established and releases all remaining air from the blood pressure cuff almost immediately.

It is to be understood that the above-described embodiments are merely illustrative of the application of the principles of this invention. Numerous variations may be devised by those skilled in the art without departing from the spirit or scope of the invention.

What is claimed is:

1. Apparatus for controlling the release of fluid under pressure from a blood pressure measuring device comprising inflatable means, source means providing said inflatable means with said fluid under pressure, a valve body having an internal chamber, means connecting said chamber and said inflatable means for fluid flow therebetween, valve means movable between a closed position and a plurality of open positions with respect to said valve body, each of said open positions permitting the escape of said fluid from said internal chamber, said valve means including a valve head, a valve seat communicating with said internal chamber and a valve element coupled to said valve head, said valve element and valve seat forming flow channels of different flow capacities corresponding to each of said open positions, and pre-settable variable control means for limiting the movement of said valve means to said open positions for providing substantially the same rate of escape of said fluid through respective ones of said flow channels for a given pressure.

2. Apparatus in accordance with claim 1 wherein said connecting means includes a passageway to permit said fluid to flow from said source means to said inflatable means and a check valve lodged in said passageway to permit the flow of said fluid out of said source means and to preclude said flow from said bore into said source means.

3. Apparatus in accordance with claim 2 wherein said valve means includes a valve stem connecting said valve head and said valve element and positioning means for normally maintaining said head in said closed position, a valve block mounted in said body having a central bore to receive said stem, wherein said valve seat is adapted to be engaged by said valve element to establish said closed position, whereby said fluid is precluded from passing from said passageway of said body to said central bore of said block.

4. Apparatus in accordance with claim 3 wherein said positioning means includes a spring having one end thereof in contact with a surface of said block, and wherein said head includes a chamber for housing said spring and having a wall in contact with the opposite end of said spring.

5. Apparatus in accordance with claim 4 wherein said spring includes means for causing said valve element to be engaged with said seat to define said closed position, and wherein said head includes means for compressing said spring and separating said valve element from said seat in response to the movement of said head toward said body to define said open positions and to provide an escape path for said fluid from said inflatable means through said passageway and said central bore and into said chamber.

6. Apparatus in accordance with claim 4 wherein said stem includes a threaded end, said head includes upper and lower segments and an escape channel to atmosphere, said upper and lower segments including a threaded bore adapted to mate with said threaded end of said stem, and said lower segment including said chamber and said escape channel, said upper and lower segments being joined integrally when said upper segment is coupled to said stem.

7. Apparatus in accordance with claim 1 wherein said valve seat and said valve element are substantially conical in shape, and wherein said body includes means for receiving said conical valve element when said valve means is moved to said open positions.

8. Apparatus in accordance with claim 1 wherein said control means includes variable position means for allowing said head to assume each of said open positions with respect to said body, each of said open positions defining a different predetermined escape rate forsaid fluid.

9. Apparatus in accordance with claim 1 including self-closing means associated with said valve means for returning said valve means to said closed position.

10. Apparatus in accordance with claim 1 wherein said open positions are established by the relative separation between said seat and said valve element when said head is brought into contact with said control means.

11. Apparatus in accordance with claim wherein said control means includes a cam rotatably mounted around said body and beneath a portion of said head, such that depression of said head brings it into contact with an edge surface of said cam.

12. Apparatus in accordance with claim 10 wherein said control means includes a truncated cylinder mounted on said body with itsaxis substantially parallel to the axis of said head, said cylinder including a control surface adapted to be engaged by a portion of said head to define a range of travel distances for said head.

13. Apparatus in accordance with claim 11 wherein said body includes a circumferential slot in a plane substantially transverse to the longitudinal axis of said body, and said cam comprises an eccentric disc fittedinto said slot.

14. Apparatus in accordance with claim 11 wherein said cam is eccentric with respect to the longitudinal axis of said body, whereby rotation of said cam about said axis establishes a range of predetermined stroke distances for said portion of said head to travel before coming into contact with said edge surface of said cam.

15. Apparatus in accordance with claim 11 wherein said cam comprises an apertured disc formed with nonuniform radial distances between its center of rotation and its outer periphery, and wherein the one of said open positions providing the maximum predetermined escape rate is established when the minimum one of said radial distances of said disc is positioned beneath said portion of said head and the one of said open positions providing the minimum predetermined escape rate is established when the maximum one of said radial distances of said disc is positioned beneath said portion of said head.

16. Apparatus in accordance with claim 15 including slot means for facilitating the rotation of said disc around said body to define a discrete predetermined escape rate for each of said radial distances which is positioned beneath said portion of said head.

17. Apparatus in accordance with claim 1 wherein said head includes means adapted to cooperate with said control means for establishing a rapid release rate for said fluid which is maintained without operator intervention after establishment and which exceeds any of the rates of escape of said fluid'through said flow channels established by said pre-settable control means.

18. Apparatus in accordance with claim 17 wherein said cooperating means includes a discrete region on a portion of said head adapted to become releasably engaged with said control means.

19. Apparatus in accordance with claim 17 wherein said head is a cylinder, said control means includes stop means for defining at least one stop position for said cylinder in moving towards said body, and said cooperating means includes a surface region on said cylinder adapted to become releasably engaged with said stop means for establishing said rapid release rate.

20. Apparatus in accordance with claim 19 wherein said cylinder further includes a housing having a spring biasing said cylinder towards said closed position and a valve stem rigid with said cylinder and connected to said valve element, said escape rates and said rapid release rate being defined by the relative separation of said valve element and said seat, wherein said stop means includes a cam mounted for rotation about said body, and wherein said surface region is a beveled portion intersecting at least the bottom surface of said cylinder, said beveled portion establishing a wedging fit with said cam to overcome the bias of said spring to establish said rapid release rate.

21. Apparatus in accordance with claim 1 wherein said valve means includes a valve stem connecting said head and said valve element, said valve seat normally receiving said valve element to establish said closed position, and wherein said flow channels are defined by the separation of said valve element and said seat, said valve element being in the shape of an inverted cone,

and said seat including a chamber having a beveled region adapted to engage at least a portion of the outer surface of said inverted cone to define said closed position.

22. Apparatus for controlling the reduction of fluid pressure in a blood pressure measuring device comprising a body having a passageway transmitting said fluid to a control location, a valve at said control location comprising a valve stem having an inverted conical end and corresponding valve seat of substantially similar inverted conical shape, a clearance channel connected to said valve seat for receiving said valve stem, and movable means including said valve stem for blocking said fluid from flowing into said channel when said inverted conical end is in contact with said seat and for allowing said fluid to flow into said channel when said inverted conical end is separated from said seat, wherein said movable means includes a valve head connected to said stem and a spring for controlling the movement of said stem between said blocking and said flow positions, and including control means for establishing a plurality of predetermined repeatable flow positions when said end and said seat are separated, the extent of said flow of said fluid being proportional to the travel of said stem from said blocking position. 

1. Apparatus for controlling the release of fluid under pressure from a blood pressure measuring device comprising inflatable means, source means providing said inflatable means with said fluid under pressure, a valve body having an internal chamber, means connecting said chamber and said inflatable means for fluid flow therebetween, valve means movable between a closed position and a plurality of open positions with respect to said valve body, each of said open positions permitting the escape of said fluid from said internal chamber, said valve means including a valve head, a valve seat communicating with said internal chamber and a valve element coupled to said valve head, said valve element and valve seat forming flow channels of different flow capacities corresponding to each of said open positions, and presettable variable control means for limiting the movement of said valve means to said open positions for providing substantially the same rate of escape of said fluid through respective ones of said flow channels for a given pressure.
 2. Apparatus in accordance with claim 1 wherein said connecting means includes a passageway to permit said fluid to flow from said source means to said inflatable means and a check valve lodged in said passageway to permit the flow of said fluid out of said source means and to preclude said flow from said bore into said source means.
 3. Apparatus in accordance with claim 2 wherein said valve means includes a valve stem connecting said valve head and said valve element and positioning means for normally maintaining said head in said closed position, a valve block mounted in said body having a central bore to receive said stem, wherein said valve seat is adapted to be engaged by said valve element to establish said closed position, whereby said fluid is precluded from passing from said passageway of said body to said cEntral bore of said block.
 4. Apparatus in accordance with claim 3 wherein said positioning means includes a spring having one end thereof in contact with a surface of said block, and wherein said head includes a chamber for housing said spring and having a wall in contact with the opposite end of said spring.
 5. Apparatus in accordance with claim 4 wherein said spring includes means for causing said valve element to be engaged with said seat to define said closed position, and wherein said head includes means for compressing said spring and separating said valve element from said seat in response to the movement of said head toward said body to define said open positions and to provide an escape path for said fluid from said inflatable means through said passageway and said central bore and into said chamber.
 6. Apparatus in accordance with claim 4 wherein said stem includes a threaded end, said head includes upper and lower segments and an escape channel to atmosphere, said upper and lower segments including a threaded bore adapted to mate with said threaded end of said stem, and said lower segment including said chamber and said escape channel, said upper and lower segments being joined integrally when said upper segment is coupled to said stem.
 7. Apparatus in accordance with claim 1 wherein said valve seat and said valve element are substantially conical in shape, and wherein said body includes means for receiving said conical valve element when said valve means is moved to said open positions.
 8. Apparatus in accordance with claim 1 wherein said control means includes variable position means for allowing said head to assume each of said open positions with respect to said body, each of said open positions defining a different predetermined escape rate for said fluid.
 9. Apparatus in accordance with claim 1 including self-closing means associated with said valve means for returning said valve means to said closed position.
 10. Apparatus in accordance with claim 1 wherein said open positions are established by the relative separation between said seat and said valve element when said head is brought into contact with said control means.
 11. Apparatus in accordance with claim 10 wherein said control means includes a cam rotatably mounted around said body and beneath a portion of said head, such that depression of said head brings it into contact with an edge surface of said cam.
 12. Apparatus in accordance with claim 10 wherein said control means includes a truncated cylinder mounted on said body with its axis substantially parallel to the axis of said head, said cylinder including a control surface adapted to be engaged by a portion of said head to define a range of travel distances for said head.
 13. Apparatus in accordance with claim 11 wherein said body includes a circumferential slot in a plane substantially transverse to the longitudinal axis of said body, and said cam comprises an eccentric disc fitted into said slot.
 14. Apparatus in accordance with claim 11 wherein said cam is eccentric with respect to the longitudinal axis of said body, whereby rotation of said cam about said axis establishes a range of predetermined stroke distances for said portion of said head to travel before coming into contact with said edge surface of said cam.
 15. Apparatus in accordance with claim 11 wherein said cam comprises an apertured disc formed with non-uniform radial distances between its center of rotation and its outer periphery, and wherein the one of said open positions providing the maximum predetermined escape rate is established when the minimum one of said radial distances of said disc is positioned beneath said portion of said head and the one of said open positions providing the minimum predetermined escape rate is established when the maximum one of said radial distances of said disc is positioned beneath said portion of said head.
 16. Apparatus in accordance with claim 15 including slot means for facilitating the rotation of said disc around said body to define a discrete predetermined escape rate for each of said radial distances which is positioned beneath said portion of said head.
 17. Apparatus in accordance with claim 1 wherein said head includes means adapted to cooperate with said control means for establishing a rapid release rate for said fluid which is maintained without operator intervention after establishment and which exceeds any of the rates of escape of said fluid through said flow channels established by said pre-settable control means.
 18. Apparatus in accordance with claim 17 wherein said cooperating means includes a discrete region on a portion of said head adapted to become releasably engaged with said control means.
 19. Apparatus in accordance with claim 17 wherein said head is a cylinder, said control means includes stop means for defining at least one stop position for said cylinder in moving towards said body, and said cooperating means includes a surface region on said cylinder adapted to become releasably engaged with said stop means for establishing said rapid release rate.
 20. Apparatus in accordance with claim 19 wherein said cylinder further includes a housing having a spring biasing said cylinder towards said closed position and a valve stem rigid with said cylinder and connected to said valve element, said escape rates and said rapid release rate being defined by the relative separation of said valve element and said seat, wherein said stop means includes a cam mounted for rotation about said body, and wherein said surface region is a beveled portion intersecting at least the bottom surface of said cylinder, said beveled portion establishing a wedging fit with said cam to overcome the bias of said spring to establish said rapid release rate.
 21. Apparatus in accordance with claim 1 wherein said valve means includes a valve stem connecting said head and said valve element, said valve seat normally receiving said valve element to establish said closed position, and wherein said flow channels are defined by the separation of said valve element and said seat, said valve element being in the shape of an inverted cone, and said seat including a chamber having a beveled region adapted to engage at least a portion of the outer surface of said inverted cone to define said closed position.
 22. Apparatus for controlling the reduction of fluid pressure in a blood pressure measuring device comprising a body having a passageway transmitting said fluid to a control location, a valve at said control location comprising a valve stem having an inverted conical end and corresponding valve seat of substantially similar inverted conical shape, a clearance channel connected to said valve seat for receiving said valve stem, and movable means including said valve stem for blocking said fluid from flowing into said channel when said inverted conical end is in contact with said seat and for allowing said fluid to flow into said channel when said inverted conical end is separated from said seat, wherein said movable means includes a valve head connected to said stem and a spring for controlling the movement of said stem between said blocking and said flow positions, and including control means for establishing a plurality of predetermined repeatable flow positions when said end and said seat are separated, the extent of said flow of said fluid being proportional to the travel of said stem from said blocking position. 